It is "just" skin irritation, but I'd leave out the "just." Basically in my case, the glue in the patches causes my skin to turn bright red and itchy underneath within moments of applying it. By the end of a week wearing it, it's purplish-red, blistering, and peeling. So I have these red itchy rash-like square marks on my body, and each one takes weeks to fade. And I have a constant itch that can't be scratched properly under wherever the patch is at the time.